This change ensures that the tables in the database during migration have at least one row of "real" data, which should help catch issues in the future where we forget to set column defaults and other such schema oversights that can only be truly tested with non-empty tables
Fixes https://jira.coreos.com/browse/QUAY-913
Unique indexes must have less than 767 bytes and UTF-8 encoding with 255
chars is beyond this maximum. Since this is an internal identifier, we
can be confident that we will not require UTF-8 for it in the future.
